Step1. Please reboot your computer and press 'F2' or 'Delete' or "F10" to enter your BIOS setup.
Step2. Looking for a tab or menu relating to booting in the BIOS setup software's opening screen. In this example, it's simply called "BOOT," and can be accessed by using the tab and/or arrow keys to highlight the word "BOOT" on the menu bar. Once there, hit enter, and you'll see a submenu that's specific to how the PC boots.
Step3. Using the tab and/or arrow keys,and select "Hard Disk Drives", and hit "Enter".
Step4. Select the "1st Drive", hit "Enter".
Step5. Select the "USB: your USB brand", in the example it is "USB: Kingston DTG(2G)", and hit "Enter" to Set the USB Flash drive as the first bootable option.
Step6. When you're done with the BIOS setup program, using the tab and/or arrow keys to navigate to the EXIT menu, select the option for saving the changes you just made, and then reboot. (In many BIOSes, a special key--often the F10 key--will save, exit, and reboot in one step.) . When your computer restarts, it will boot from the USB flash drive.